DurationField format in a ModelForm

Question

I have a Django model that contains a duration field:

class Entry(models.Model):
    duration = models.DurationField()

And I want to render a form for this model using a ModelForm:

class EditEntryForm(forms.ModelForm):
    class Meta:
        model = Entry
        fields = ['duration']

Which is all working. However, if editing an existing model, the duration rendered in the text box is of the format HH:MM:SS

I will never be dealing with durations over an hour. How can I change how Django is formatting this field in the form to just be MM:SS?

I already have a custom template filter in use when rendering the model, I just can't figure out how to change how the form is rendered.

Thanks

Answer 1

You should be able to do this by providing a custom widget for the field:

from django.forms.widgets import TextInput
from django.utils.dateparse import parse_duration

class DurationInput(TextInput):

    def _format_value(self, value):
        duration = parse_duration(value)

        seconds = duration.seconds

        minutes = seconds // 60
        seconds = seconds % 60

        minutes = minutes % 60

        return '{:02d}:{:02d}'.format(minutes, seconds)

and then you specify this widget on the field:

class EditEntryForm(forms.ModelForm):
    class Meta:
        model = Entry
        fields = ['duration']
        widgets = {
            'duration': DurationInput()
        }

Of course, this will cause weirdness if you do ever supply durations longer than an hour...